The hungrier the child, the more zinc shortened the diarrhoea
In malnourished children it took about 26 hours off. In children over six months generally, about 11 hours. Under six months it did nothing at all.
What the study found
Zinc shortened diarrhoea most in the worst-nourished children
In malnourished children it took about 26 hours off, on high-certainty evidence. In children over six months generally, about 11 hours, and the certainty falls to low. Under six months it did nothing, and the estimate points the wrong way. The benefit tracks the deficit.
The caveat · Mostly Asian trials, zinc often low
Most of these trials ran in Asian countries where zinc shortage is common, and the review's authors say plainly that the evidence does not support giving zinc to well-nourished children or in low-risk settings. Vomiting rose in both age groups, by about 57% in the over-sixes, which is a real cost in a child already losing fluid. Death and hospitalisation, the outcomes that matter most, sit at very low certainty and are not settled here.